“This is of serious concern, the apparent enforced disappearance of Mr. Khashoggi from the Saudi Consulate in Istanbul,” Ravina Shamdasani, a spokeswoman for the human rights office, told reporters in Geneva.

The Sabah newspaper reported that, “Two Gulfstream IV-type private planes took off from Riyadh on Oct. 2 and landed at Ataturk Airport; one of them before Khashoggi entered the consulate, the other one after he entered.” The report added that the two jets belonged to Sky Prime Aviation Services, a charter company based in Riyadh that has long worked with the Saudi government.

The newspaper reported that one jet, with tail numberHZ-SK2, landed at Ataturk Airport, which serves Istanbul, at 3:13 a.m. that day, hours before Mr. Khashoggi entered the consulate just after 1 p.m.

The second plane, with tail number HZ-SK1, landed at Ataturk Airport at 5:15 p.m. on the same day, and then took off barely an hour later, at 6:20 p.m., the newspaper reported, adding that the vessel flew to Egypt and, the next day, back to Riyadh, the Saudi capital.

The jet that had arrived earlier left Istanbul at 10:46 p.m. on Oct. 2, flying to Dubai and then to Riyadh, according to the newspaper. The people who had arrived on that plane checked into two hotels near the Saudi Consulate, booking rooms for three nights, but they retrieved their belongings and left the same day, Sabah reported.

The group in the second plane went directly to the consulate and then back to the airport.

Sabah reported that it had obtained passenger lists for both aircraft. It did not publish the names, but it said they were Saudi officials and intelligence officers. There were nine passengers on the first plane and six on the second, and a total of seven crew members on both jets, the newspaper reported.